Hard disk drive head-media system having reduced stiction and low fly height

ABSTRACT

A head and disk system for use in a disk drive is disclosed. The head includes a slider having a surface that contacts the disk. This disk contacting surface of the slider is textured with pads, bumps, an etched surface or an otherwise roughened surface. The contact area of the disk has a greater roughness than a data zone. The head disk system exhibits acceptable stiction. Additionally, low glide avalanche over the CSS zone, thus enabling low fly height, is achieved.

FIELD OF THE INVENTION

[0001] The present invention relates to hard disk drives used to storedata, and more particularly to a head-media system having reducedstiction and low fly height capability.

BACKGROUND OF INVENTION

[0002] In the field of hard disk storage systems, continuousimprovements have been made in increasing the areal density, i.e., thenumber of stored bits per unit of surface area. As is well known,decreasing the fly height of the read/write head results in reducedpulse width (PW50) due to a number of factors which allows for greaterrecording density. For a discussion of the effects of lower fly height,see, for example, U.S. Pat. No. 5,673,156. In any event, bringing thehead closer to the media has been a key area of effort in increasingrecording densities.

[0003] The read/write head is typically a part of or affixed to a largerbody that flies over the disk and is typically referred to as a“slider”. The slider has a lower surface referred to as the air bearingsurface. The air bearing surface typically comprises one or more railswhich generally generate a positive air pressure. In addition, there isoften a cavity or similar structure that creates a sub-ambient pressureto counterbalance the positive pressure to some extent. The slider bodyis attached to a suspension via a head gimbal assembly which biases theslider body towards the disk. The net effect of the air bearing surfaceand the suspension is to cause the slider to fly at the desired heightwhen the disk is at full speed, and to cause the slider to be in contactwith the disk surface when the disk is at rest. The portion of theslider that contacts the disk is typically the aforementioned one ormore rails. As the fly height of the slider is reduced, it is necessaryto produce disks with increasingly smooth surfaces. As is well known,the slider undergoes sliding contact with a portion of the disk wheneverthe drive motor is turned on or off. This contact between the slider andthe disk occurring when the drive is turned on and off is known ascontact start stop (CSS) operation.

[0004] The CSS motion between the slider and the disk is of greatconcern in the reliability of the drive since it is generally the majorinitiator of failure in hard disk drives. In today's commerciallyavailable disk drives, generally 20,000 CSS cycles for desk-top computerapplications and up to 100,000 CSS cycles for portable or hand-heldcomputer applications is considered adequate. A greater number of CSScycles is needed in portable and hand-held computer applications becausethe drives are frequently turned on and off to conserve battery power.Recently, there has been a trend to reduce power consumption in desktopcomputers. Therefore it is expected that CSS requirements will greatlyincrease for desktop applications as well.

[0005] In order to improve the CSS performance, it is well understoodthat friction must be minimized between the slider and the disk. Staticfriction or stiction is a term used to describe the force exertedagainst the motion of the slider relative to the disk surface when theslider is at rest on the disk surface. Stiction values are often givenin grams to represent the force required to separate the slider from thedisk. The stiction is greatly increased if the lubricant that is used onthe surface of most disks wets a significant portion of the slider/diskinterface.

[0006] Often, the term initial stiction refers to the stictionencountered when the slider contacts the disk for a minimal amount oftime, without a significant opportunity for lubricant to migrate to theslider/disk interface. Parking stiction is a term used when the diskdrive has not been in use, so that the slider has been at rest on theCSS zone for some time and may have some lubricant migration to theinterface. Parking stiction is typically greater than initial stiction.Finally, the term fly stiction is used to describe the situation wherethe slider has flown over the disk for a considerable amount of time soas to pick up lubricant, and then after returning to the disk surfacehas remained on the disk surface for a sufficient time to allow thelubricant to flow to and significantly wet the interface, therebygreatly increasing stiction. Stiction can be strong enough to preventthe drive motor from turning, or worse yet, can damage the head, causethe slider to become detached from the suspension assembly, or cause theslider to ding the disk surface during separation of the slider from thedisk surface. (The term “ding” is used in the art to describe anabnormal and sudden impact of the slider against the disk surface whichdents the disk surface around the impact area. This can occur, forexample, by accidentally dropping the disk drive on a hard surface. Thiscan also occur when the slider is stuck on the disk surface during drivestart-up due to high stiction, followed by sudden release of the slider,which causes it to bounce on and thereby dent the disk surface.)

[0007] It has been recognized that stiction can be reduced by putting a“micro-texture” on the disk surface to reduce the effective contact areabetween the slider and the disk. See, for example, Marchon et al.,“Significance of Surface Roughness Measurements. Application to theTribology of the Head/Disk Interface,” Tribology and Mechanics ofMagnetic Storage Systems VI, ASLE SP-26, page 71 (1990), which describesthe roughness needed to achieve an acceptable rate of increase instiction under prolonged CSS for a disk comprising an aluminum/NiPsubstrate with a near concentric texture pattern. Also, Lee et al.,describe the effect of texture crossing angle on CSS performance in“Effect of Disk Cross Hatch Texture on Tribological Performance”,published in IEEE Transaction on Magnetics, Vol. 28, No. 5, September1992, pp. 2880-2882. In effect, a rougher texture and modification oftexture morphology is needed to achieve acceptable CSS performance. Thetexture pattern may be put on the disk by mechanically abrading thesubstrate surface using well known methods.

[0008] In contrast to the requirements of CSS operation, for reading orwriting data it is desirable that the surface of the disk be as smoothas possible to allow the head to fly as close as possible to the disksurface. Because of these differing requirements, it is known to usezone texturing where a portion of the disk used for CSS operation (theCSS zone) is textured more heavily than the portion of the disk used fordata storage (the data zone). One problem with such zone texturing,however, is that it is difficult to create a precisely delineated CSSzone with mechanical texturing methods. Because of this, some portion ofthe data zone is typically lost, thus reducing the amount of data a diskcan hold.

[0009] Because the data zone is smoother than the CSS zone, both theglide height (minimum distance at which a slider may fly withoutcontacting any portion of the disk surface) and the glide avalancheheight (distance above mean disk surface level at which the slider makesregular and continuous contact with the disk surface) are lower in thedata zone than in the CSS zone. However, because it is necessary to movethe head from over the data zone to the CSS zone, the glide avalancheheight of the CSS zone limits the fly height over the data zone, as thehead must be able to safely move between the two zones, without unduecontact in the CSS zone which could lead to wear of the disk surface,the slider, and generation of debris. It should be noted that it isdifficult to produce mechanical texturing with a high degree ofuniformity. This nonuniformity in surface texture means that someportions of the CSS zone may be considerably rougher than average, whichposes further limitations on the fly height.

[0010] Another known method to provide the necessary texture in the CSSzone is laser zone texturing. An example of this method is described inU.S. Pat. No. 5,108,781. n such a method, a laser beam is focused to asmall spot on the disk surface, forming uniformly shaped and sizedfeatures in a controllable pattern. Because of the high degree ofcontrol possible with a laser system, the CSS zone can be preciselydelineated so that loss of data zone area can be minimized. Furthermore,because the size of the features is better controlled than the surfacemorphology resulting from mechanical texturing, the above-describeduniformity problem is greatly reduced. However, because the surface inthe laser texture zone has a considerably greater roughness than thedata zone, the CSS zone still provides a limitation to the fly heighteven in laser zone textured disks. See “The Special Needs of ServerClass Drives” by Wachenschwanz et al., IDEMA Insight, Vol. XI, No. 1,January/February 1998 which illustrates that laser zone texturingachieves acceptable stiction performance for today's devices and furtherasserts that laser based zone textured disks should be extendible for atleast two generations.

[0011] Another method to reduce stiction in CSS operation is to providea texture on the surface of the slider rather than the disk. Suchsliders are frequently referred to as “padded” sliders or“stiction-free” sliders. The texture may be provided in a variety ofmanners. For example, “Numerical Simulation of the Steady State FlyingCharacteristics of a Fifty Percent Slider with Surface Texture” by Wahlet al., IEEE Transactions on Magnetics, Vol. 30, No. 6, November 1994,discloses a slider having a plurality of hemispherical, conical, orcylindrical features arranged in a densely packed pattern thereon. U.S.Pat. No. 5,079,657 teaches several varieties of textured sliders usingchemical etching in one embodiment formed by differential etching, andin another embodiment formed by the use of a masked photo resist layer.“Stiction Free Slider for Lightly Textured Disks”, by D. Yamamoto etal., IEEE Trans. Mag. Vol. 34, No. 4, 1998, shows a textured sliderwhich has one or more “pads” along the length of each rail. Herein, aslider having texture formed by any method, including the foregoing,with any type of pattern is referred to as a “textured” slider.

[0012]FIGS. 1A and 1B show two examples of textured sliders. As shown inFIGS. 1A and 1B, the sliders comprise a slider body 101 a/b coupled tosuspension 102 a/b. Each of the sliders comprises two rails 103 a/b(although sliders with a single rail and sliders with more than tworails may be used). Also as shown in FIGS. 1A and 1B, each of the railshas a plurality of pads 104 a/b. In the particular slider shown in FIG.1B, each pad 104 b may have dimensions, for example, of approximately35-50 microns wide by 50-100 microns long. Of course other dimensionsmay be used.

[0013] In the above described textured sliders, the intent is to providea slider surface that has some portions at a different elevation thanothers to reduce the total contact area and thereby reduce stiction. Oneadvantage to using such sliders is that a lower roughness of the disksurface is needed to meet stiction requirements. This lower roughness iscomparable to the roughness of current data zone texture, so that theentire disk surface may be textured as appropriate for data storage,thus allowing for lower fly heights and increased density. Additionally,textured sliders are intended to eliminate the need for a separate zone,whether by mechanical texturing with its concomitant loss in usablearea, or laser zone texturing which typically adds a step to the diskfabrication process. In the above mentioned article by Yamamoto et al.,it is stated that the stiction results obtained with the stiction freeslider described therein is acceptable even on relatively lightlytextured surfaces which have a roughness comparable to current data zonetexture. Recently, it has been reported that a textured slider may beextendible for the next several generations of disk drives. See“Fujitsu's Padded Slider Hold Stiction at Bay”, Data Storage, May 1998,page 8.

[0014] A further approach to the stiction problem is drives using aso-called “load/unload”mechanism. In these drives, when the drive isturned off, the head is parked on a ramp and not on the disk surface.Therefore, in load/unload drives, the problem of stiction is eliminated.However, the load/unload mechanism adds to the cost and complexity ofthe drive.

[0015] As can be seen from the foregoing, current attempts are to eitherimprove the disk texturing, with particular current emphasis on laserzone texturing or alternatively to eliminate the need for a separatezone by providing a textured slider or by providing a load/unloadmechanism.

[0016] As recording density increases, ever smoother surfaces will berequired so that heads may fly lower. Current state-of-the-art systemshave glide avalanche heights in the data zone of approximately 0.8through 1.0 microinch (μ″). In the future, glide avalanche heights ofapproximately 0.4 μ″ or below will be needed for disks having densitiesin the range of approximately 3-5 gigabits per square inch (Gb/in²). Ona laser zone textured disk, the glide avalanche height for such CSS zonewould need to be in the range of approximately 0.6-0.7 μ″ An averagelaser bump height in the range of approximately 50-100 angstroms (Å)will provide a glide avalanche height in this range, but is likely tohave unacceptably high stiction for conventional sliders. Thus, what isneeded is a method and apparatus for providing a slider-head systemhaving very low glide height and acceptable stiction performance.

SUMMARY OF THE INVENTION

[0017] An embodiment of the present invention comprises a slider and adisk for storing magnetic data. The slider is textured to reducestiction. The disk has a contact area for CSS operation (CSS zone)having a surface roughness greater than that of an area for datastorage. The surface roughness may be created by any means such asmechanical texturing, top surface texturing, sputter texturing, or maycomprise a pattern of features with relatively uniform height such asthose formed by laser texturing. The CSS zone can be made with asufficiently low average height to allow for the low fly heights ofadvanced disk drives. By use of a textured slider and a disk having, forexample, laser features in the CSS zone, stiction is kept sufficientlylow to allow for reliable operation.

[0018] Other features and advantages of the present invention willbecome apparent from the detailed description, figures and claims whichfollow.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIGS. 1A and 1B show two exemplary types of textured sliders.

[0020]FIG. 2 shows glide avalanche height as a function of surfaceroughness.

[0021]FIGS. 3A and 3B illustrate the data zone and the CSS zone,respectively, of a laser textured disk.

[0022]FIG. 4 shows glide avalanche height as a function of average bumpheight for a laser textured disk.

[0023]FIG. 5 shows initial stiction results for a textured slider on alow roughness mechanically textured surface, and on a laser texturedsurface.

[0024]FIGS. 6A, 6B, and 6C show initial stiction over 10,000 cycles fora textured slider on a mechanically textured surface of a firstroughness, a mechanically textured surface of a second roughness, and alaser textured surface, respectively.

[0025]FIG. 7 shows initial stiction as a function of glide avalancheheight for an embodiment of the present invention.

[0026]FIG. 8 shows stiction results over 10,000 cycles for a texturedslider on mechanically textured surfaces and on a laser texturedsurface.

[0027]FIGS. 9A and 9B show stiction as a function of glide avalancheheight for a conventional slider and for an embodiment of the presentinvention, respectively.

[0028]FIG. 10 shows contact area of the slider surface as function ofslicing depth.

DETAILED DESCRIPTION

[0029] A head-media system comprising a textured slider and a diskhaving a CSS zone with a greater roughness than a data zone. In thefollowing description, numerous specific details are set forth such asspecific sliders, disks, roughness values, etc. It will be appreciated,however, that these specific details need not be employed to practicethe present invention. In other instances, well known methods andapparatuses are not described in detail in order not to obscureunnecessarily the present invention.

[0030] As described earlier, one important parameter is the glideavalanche height which is the height at which the lowest portion of theslider begins to make regular contact with the disk. Typically, theglide avalanche is stated as distance above the average surface height,typically expressed in microinches. Referring to FIG. 2, a graph ofsurface roughness (RMS Roughness) versus avalanche height for amechanically textured disk surface is shown. As expected, as the surfacegets smoother, the glide avalanche is reduced. As is well known in theindustry, a lower glide avalanche point is needed for lower fly heights.It is believed that in disks having a density in the 3-5 Gb/in² range,the glide avalanche in the data zone will need to be approximately 0.4μ″. Although the CSS zone need not have as low a glide avalanche as thedata zone, it too must be reduced to enable lower fly heights over thedata zone, because too great a disparity in glide avalanche between thetwo areas would cause excessively severe wear on the slider as the headis moved back and forth, as described previously. For disks having theaforementioned 3-5 Gb/in² density, it is believed that the glideavalanche height in the CSS zone should be in the range of approximately0.6-0.7 μ″. Referring to FIG. 2, it can be seen that to meet the aboverequirements the data zone would need to have a maximum RMS roughness ofapproximately 10-15 Å, and the CSS zone would need to have a maximum RMSroughness of approximately 35 Å.

[0031] Also as described earlier, it is preferable not to have twomechanically textured zones because it drastically reduces the amount ofspace for storing data, and adds to process complexity. A disk texturedin its entirety with the requisite low roughness needed for advanceddensities would therefore require a surface roughness of about 15 Å RMSor lower, which corresponds to an Ra roughness of approximately 12 Å orlower.

[0032] Referring to FIG. 3A, a portion of the data surface of a disk isshown. As can be seen, the surface 300 has mechanical texturing thereon.FIG. 3B shows the CSS zone of the same disk where laser zone texturingwas used. As can be seen, the surface still has mechanical texturing 300as well as numerous laser features 301 thereon. The laser features 301shown in FIG. 3B are generally circular, crater shaped features. It willbe appreciated that other types of laser features such as the so-called“sombrero” type, or other shapes of the laser features may be used inthe below described embodiments of the present invention utilizing lasertexture. Typical horizontal dimensions of laser features, for examplemeasuring from one side of the rim to the other, are in the range ofabout 1 micron through several microns. It will be appreciated of coursethat dimensions outside this range may be used in the present inventionas well. The average height of the features 301 above the surface 300 isapproximately 200-300 Å in most state of the art devices.

[0033] Referring now to FIG. 4, a graph of bump height as measured by anatomic force microscope (AFM) versus the glide avalanche is shown. Ascan be seen, a bump height in the range of approximately 200-250 Åresults in a glide avalanche of approximately 0.85-1.1 μ″. While thisglide avalanche is acceptable for the CSS zone of current devices, asnoted above a much lower glide avalanche will be required for futuredevices. For example, to achieve a glide avalanche of approximately 0.6μ″, an average bump height of approximately 100 Å is needed.

[0034] As will be seen it has been found by the present inventors thatthe use of a textured slider on a very lightly textured disk (e.g.,avalanche height of about 0.4 μ″) may encounter stiction problems afteruse. Furthermore, although considerable effort is being expended toproduce textured sliders for current and future requirements,considerable development work remains. Similarly, with respect to lasertexture, significant effort will be required to provide features havinga low enough height for glide avalanche requirements without poorstiction performance. It would be desirable to provide for good stictionperformance at low glide avalanche heights utilizing currentlymanufacturable technology for current and future devices. Furthermore,it would be desirable that the system be robust to provide an acceptableoperating window.

[0035] To overcome these problems, the present invention comprises theuse of a textured slider together with a disk having a separate zonehaving a greater roughness than the data zone. In one embodiment, amechanically textured zone may be used if desired. Although thisembodiment would still have the above described problems of mechanicallyzoned disks of the prior art, i.e. loss of some of the surface area ofthe disk for data storage, and greater nonuniformity than lasertexturing, such an embodiment achieves improved stiction results ascompared with a textured slider used on a disk textured entirely as isneeded for the data zone. Alternatively, other methods of texturing maybe used such as texture provided by sputtering, top surface texturingwherein the carbon overcoat is in some way treated to provide a texture,by various patterning methods to provide features, or as described indetail herein, by a method such as laser texturing.

[0036] In a particularly preferred embodiment, the invention comprises adisk having a zone that is textured by forming a plurality of featuresof uniform height, such as features formed by use of concentratedradiation in the CSS zone. For purposes of discussion, the latterembodiment will be discussed in conjunction with laser texturing forillustration. It will be appreciated, however, that any method offorming features with this morphology i.e. texture by way of discreetand relatively uniform protrusions, as opposed to random surfacetexturing characteristic of mechanical texturing processes and somechemical texturing processes, will provide the benefits of thisembodiment. As will be seen, by use of this method, stiction resultsapproximately equivalent to results achieved with a stiction-free sliderwhen used on a mechanically textured surface of high roughness areachieved. Because of the use of a textured slider, the average laserfeature height can be very low, such as 100 Å for disks storingapproximately 3-5 Gb/in² and lower heights for capacities beyond thisrange, without encountering the above described stiction problems ofsuch small bumps. Because the glide avalanche height of such bumps isrelatively small, the disk may be used in high density applications.

[0037] Referring to FIG. 5, a bar graph of stiction in grams is shown.The texture on the slider comprised a pattern of small protrusions orbumps over most of the surface of the rails such as is shown in thearticle by Wahl et al. Herein, such textured sliders will be referred toas “full texture” sliders. FIG. 5 shows the stiction for this slider onseveral different disk surfaces. Bar 501 shows the initial stiction on amechanically textured portion of a disk having a glide avalanche of 0.5μ″. As can be seen, the amount of stiction is clearly within anacceptable range. Bar 502 shows the stiction in another mechanicallytextured region having a glide avalanche of approximately 0.45 μ″, andagain as can be seen the stiction is acceptable. Bars 503 and 504 showthe stiction in two more mechanically textured locations on the disk,both with a glide avalanche height of 0.45 μ″. However, the locationsrepresented by 503 and 504 show the stiction results after the sameslider has undergone a few hundred CSS cycles. As can be seen, thestiction has now gone well above acceptable limits and is now in therange of approximately 13-20 grams. This data suggests that some type ofdegradation in the condition of the slider surface occurs after asignificant number of CSS cycles. It appears that the condition of thedisk does not cause the degradation as each bar represents a newlocation on the disk. This head degradation significantly degrades thestiction performance on very smooth surfaces.

[0038] Referring now to Bars 505, 506, 507, and 508 stiction resultsusing the same slider that was used to produce Bars 501-504 is shown.The data for Bars 505-508 was generated with this slider after it hadgenerated the data for Bars 501-504 so that the slider at this point hashad considerable degradation. Bars 505-508 represent stiction resultsfrom laser textured disk surfaces that have glide avalanche heights of0.60 μ″, 0.65 μ″, 0.85 μ″ and 1.20 μ″ respectively. The patterns of thelaser features were 25 μm×25 μm, 20 μm×20 μm, 20 μm×40 μm, and 50 μm×50μm, respectively, where the first number represents the spacing offeatures along the track i.e. in the circumferential direction, and thesecond number represents the spacing of the features radially. As can beseen, in all cases the stiction remained at acceptable levels, eventhough the textured slider had degraded considerably such that thestiction rose to high levels in very smooth regions.

[0039] As noted earlier, the CSS zone needs to have a glide avalanche inthe range of 0.6-0.7 μ″ or less in the next couple of generations ofdrives. As can be seen from Bars 505 and 506, which represent zones withglide avalanche heights of 0.60 and 0.65 μ″, the present inventionprovides acceptable stiction results for future devices. Referring backto FIG. 4, as can be seen, the average bump height to achieve this glideavalanche is approximately 100 Å. Thus, the height of the laser featuresis much lower than currently being used in laser textured disks whichuse greater average heights to avoid stiction problems.

[0040] Referring again to FIG. 5, it will be noted that the glideavalanche of the slider/disk system of the present invention (Bars505-508) is at a higher glide avalanche than the mechanically texturedregions shown in Bars 501-504 which have a smooth surface characteristicof data zone regions. In embodiments using a mechanically textured CSSzone, the mechanically textured region should have a similar glideavalanche as the laser texturing used in FIG. 5 to achieve comparableresults. However, importantly, the laser texture embodiment avoidshaving the need to produce a mechanically zoned disk that loses valuabledata storage area. In any embodiment, the present invention avoidshaving to limit the data zone roughness by the higher roughness neededfor acceptable stiction performance in future devices.

[0041] FIGS. 6A-6C illustrate the improvement achieved with the presentinvention. FIGS. 6A-6C show initial stiction in grams versus cyclenumber, for 10,000 cycles. The textured slider used in FIGS. 6A-6C wasagain a full texture slider. In the graph of FIG. 6A, the slider wasused on a very smooth mechanically textured surface. The surface had aroughness Ra in the range of approximately 10 Å and a glide avalancheheight of approximately 0.4-0.5 μ″. As can be seen, the stiction quicklyexceeded 10 grams after several cycles, and exceeded 30 grams after acouple thousand cycles.

[0042]FIG. 6B shows initial stiction for a textured slider on amechanically textured surface having an average roughness Ra ofapproximately 16 Å. As can be seen, by using a higher roughness thestiction results are greatly improved with the stiction being slightlyover 10 grams after 10,000 cycles. The results can be further improvedby providing an even rougher surface in the CSS zone. Note that theroughness of approximately 16 Å is much lower than the approximately 35Å roughness upper limit needed for the CSS zone for producing systems inthe 3-5 Gb/in² range. Thus, FIG. 6B illustrates the benefits of amechanically textured zone having a roughness greater than the datazone.

[0043] Referring to FIG. 6C, the stiction versus cycle for 10,000 cyclesfor a disk having laser features thereon is shown. In the graph of FIG.6C, the CSS zone had laser textured features with an average height ofapproximately 85 Å and a glide avalanche height of approximately 0.6 μ″.As can be seen, the typical stiction value is well under 5 grams (withthe exception of 1 parking stiction event as shown by the spike in thegraph) for the entire 10,000 cycles. The average initial stiction inFIG. 6C after 10,000 cycles was approximately 2.3 grams. The maximumstiction, other than the parking event, was 4.5 grams. This comparesparticularly well to the first 10,000 cycles of FIG. 6A. In comparingthe graphs, note the scale difference in the Y axis.

[0044]FIG. 7 further shows the results of the present invention. Shownin FIG. 7 is the average initial stiction in grams versus the avalancheheight for a full texture head on a laser textured surface. As can beseen, by use of the present invention the stiction can be kept toacceptable levels even when the glide avalanche is below 0.5 μ″. Thus,the present invention will allow for acceptable stiction performance ondisks having low glide avalanche in the CSS zone, as required by future3-5 Gb/in² devices and beyond.

[0045]FIG. 8 again shows the improvement achieved with the presentinvention. Curves 801, 802, 803, and 804 show stiction in grams as afunction of CSS cycle. The slider design used in all of Curves 801-804was a four pad design similar to the design illustrated in FIG. 1B, withtwo of the pads 104 b on each of two rails. Curves 801 and 802 show theresults for the slider when used on a mechanically textured surfacehaving an Ra roughness of approximately 10 Å. As can be seen, theinitial stiction is marginal at about 5 grams and after approximately100 cycles increases up to approximately 10 or more grams, whichincrease is believed to be due to head degradation as described earlier.Curve 803 was generated using the same type of slider but on amechanically textured surface having an Ra roughness of approximately 20Å. As can be seen, the stiction behavior is generally very good.Finally, Curve 804 was generated with the same type of slider but on aCSS zone having laser features. The laser features had an average heightof approximately 85 Å and a glide avalanche height of approximately 0.6μ″. As can be seen, even after 10,000 cycles, the stiction remainedbelow 2 grams. It should be further noted with respect to curves 803 and804 that not only do these embodiments of the present invention achievelow stiction, but the stiction remains low over many cycles, indicatingthat the present invention is relatively insensitive to degradation ofthe textured slider.

[0046] As shown in FIGS. 5-8, the present invention provides for reducedstiction when using a textured slider on a CSS zone in accordance withthe present invention. FIGS. 9A and 9B illustrate the improvement of thepresent invention as compared with a non-textured slider. Firstreferring to FIG. 9A, a graph of avalanche height versus stiction ingrams is shown. In FIG. 9A, curve 901 shows the results for theconventional slider on a laser textured surface and the Curve 902 showsthe conventional slider on a mechanically textured surface. As can beseen, the stiction with a conventional head on a laser textured surfacetypically reaches unacceptable values at a glide avalanche height ofaround 0.8 μ″. The stiction on the mechanically textured surface reachesunacceptable levels at approximately 0.7 μ″. The stiction response isgenerally more gradual on the mechanically textured surface as comparedwith the laser textured surface because the laser textured surfacegenerally has peaks with relatively uniform heights, so that the surfacearea contacted increases much more rapidly on a laser textured surfaceas the slider is moved closer to the disk.

[0047] Referring now to FIG. 9B, a graph of avalanche height versusinitial stiction for a full texture slider is shown. Curve 905 shows theresults for the textured slider on a mechanically textured surface. Ascan be seen, the stiction results are improved over FIG. 9A by virtue ofthe use of the textured slider. Curve 906 shows the stiction results forthe textured slider on a surface having laser texturing. As shown bycurve 906, the use of a textured slider on a CSS zone having laserfeatures dramatically improves the initial stiction. As can be seen, incontrast to FIG. 9A the stiction remains under 5 grams at 0.8 μ″ glideavalanche height and on average remains below this value to about 0.4 μ″glide avalanche height.

[0048]FIG. 10 shows a bearing ratio curve for several types of sliders.The curves show the percent of the slider area in contact with thesurface as a function of distance from the disk surface. The chart showsthe contact area in mm² of the slider as a function of slicing depthinto the surface of the slider i.e. a depth of zero indicates the firstpoint of contact with greater contact at greater slicing depths. Curves1001, 1002, and 1003 show current designs having a contact area ofapproximately 1.4 mm². Curves 1005-1010 show so called “pico” sliderswhich have a reduced form factor and have a lower total contact area ofapproximately 0.6 mm² used in advanced designs. The curves 1009 and 1010represent curves for textured sliders. Because the sliders have sometype of texture, the area increases very slowly with slicing depth ascompared with non-textured sliders. It has been found that the presentinvention works well with all types of textured sliders. In particularhowever, the best results appear to be obtained with sliders that havenumerous point contact areas such as that shown in the article by Wahlet al., or other sliders with multiple points of low surface areacontact such as some of the sliders shown in U.S. Pat. No. 5,079,657, orsliders according to the teachings of U.S. Pat. No. 5,673,156. It willbe appreciated that any textured sliders including the foregoing, orsliders having a combination of the various types of textures, such as apattern of small protrusions in one portion, and a single large area padin another, may be used in the present invention.

[0049] The laser features on the disk in laser texture embodiments weremade and formed using conventional patterns. As described herein, thetypical average height of the laser texture features may be much lessthan is used with a non-textured slider. For example, laser features inthe range of approximately 50 Å-150 provide for lower glide avalanche,needed to improve fly height in the data zone. Further, reduced laserfeature height may be used in future devices requiring even lower glideavalanche height. However, by use of a textured slider, the stiction isconsiderably reduced compared with that which would be obtained by useof a conventional slider on such small laser features.

[0050] In designing the laser texture pattern one consideration is thatthe pattern should be such to ensure that the textured surface contactsthe laser features. For example, in the padded slider shown in FIGS. 1Aand 1B, the radial spacing between the laser features should be lessthan the width of the narrowest pad, (e.g., less than approximately35-50 μm radial spacing for the exemplary dimensions given inconjunction with FIG. 1B) so that it is ensured that each pad lands on alaser feature. Similarly, the distance between each laser feature in thecircumferential direction should be no more than the length of theshortest pad (e.g. less than approximately 50-100 μm circumferentialspacing for the exemplary dimensions given in conjunction with FIG. 1B).In this way, the elevated portions on the slider are ensured to contactthe texture features on the disk to minimize surface area contact andtherefore stiction. As used herein, the higher or greater elevation on aslider is considered to be a portion closer to the disk surface thanother portions. For sliders that comprise texturing over a greater area,such as sliders having a plurality of protrusions over the entiresurface and sliders with stripes and bars, the laser feature pattern canbe less dense than for the sliders having a limited number of pads.

[0051] While the invention has been described with respect to specificembodiments thereof, those skilled in the art will recognize thatchanges can be made in form and detail without departing from the spiritand scope of the invention. The use of a textured slider and a diskhaving a CSS zone with a rougher texture provides the ability to achievelow fly heights, while achieving acceptable stiction in the CSS zone. Inone embodiment, a texture comprising precisely placed features ofuniform height, such as those formed by radiant energy focused to a spoton the disk, is used. The precise placement allows for a preciselydelineated CSS zone maximizing area usable for data storage. The gooduniformity reduces the margin that must be added to the fly height toaccount for the highest peaks in the CSS zone. Preferably, the ±3 sigmauniformity is approximately ±20%, more preferably ±15% and mostpreferably ±10% or better. Although the latter embodiment has beendescribed using laser texture features, any type of method that producesa similar morphology, such as use of concentrated radiant energy, orother methods, such as by performing a patterning and etch step on thedisk surface, achieves these advantages. However, any type of texturemay be used in the CSS zone provided it is sufficiently rough to achievethe stiction performance described herein. Furthermore, as mentionedearlier, numerous types of textured sliders may be used. The embodimentsdescribed herein, as well as embodiments having such changes in form anddetail come within the scope of the present invention.

What is claimed is:
 1. A system for storage of data comprising: a bodycapable of flying over a disk; a disk capable of storing data; said bodycomprising a first surface, said first surface in sliding contact with acontact surface of said disk during at least a portion of an operationof said system, said first surface having a texture thereon such thatsome portions of said surface are at a different elevation than otherportions thereof; and said disk comprising at least two zones includinga first zone comprising said contact surface and having a firstroughness, and a second zone comprising a data storage region and havinga second roughness, said first roughness being greater than said secondroughness.
 2. The system as described in claim 1 wherein said roughnessin said first zone is created by one of mechanical texturing, topsurface texturing, sputter texturing, and application of concentratedradiant energy.
 3. The system as described in claim 1 wherein saidroughness in said first zone is provided by features comprising apattern of protrusions of substantially uniform height.
 4. The system asdescribed in claim 3 wherein said features are formed by applyingconcentrated radiant energy.
 5. The system as described in claim 4wherein said features formed by concentrated radiant energy comprisefeatures formed by applying pulsed laser energy to said contact surface.6. The system as described in claim 3 wherein said features are providedin a pattern such that portions of said first surface at greaterelevations than other portions contact said features when said firstsurface contacts said disk on said contact surface.
 7. The system asdescribed in claim 1 wherein said texture of said first surfacecomprises one or more of: pads, bumps, stripes and bars.
 8. The systemas described in claim 1 wherein said features have an average height ofapproximately 100 Å or less.
 9. The system as described in claim 8wherein a stiction value is lower than that obtained in a second systemhaving said features with said average height wherein said second systemcomprises a second slider without said texture thereon.
 10. A disk drivecomprising said system of claim
 1. 11. A method for storage of datacomprising: providing a body capable of flying over a disk; providing adisk capable of storing data; moving said body over said disk in slidingcontact with said disk during a portion of an operation; providing onsaid body a first surface having a texture thereon such that someportions of said first surface are at a different elevation than otherportions thereof; and providing on said disk at least two zonesincluding a first zone comprising a contact surface and having a firstroughness, and a second zone comprising a data storage zone and having asecond roughness, said first roughness being greater than said secondroughness.
 12. The method as described in claim 11 wherein saidroughness in said first zone is created by one of mechanical texturing,top surface texturing, sputter texturing, and application ofconcentrated radiant energy.
 13. The method as described in claim 11wherein said roughness in said first zone is provided by featurescomprising a pattern of protrusions of substantially uniform height. 14.The method as described in claim 13 wherein said features are formed byapplying concentrated radiant energy.
 15. The method as described inclaim 14 wherein said features formed by concentrated radiant energycomprise features formed by applying pulsed laser energy to said contactsurface.
 16. The method as described in claim 13 wherein said featuresare provided in a pattern such that portions of said first surface atgreater elevations than other portions contact said features when saidfirst surface contacts said disk on said contact surface.
 17. The methodas described in claim 11 wherein said texture of said first surfacecomprises one or more of: pads, bumps, stripes and bars.
 18. The methodas described in claim 11 wherein said features have an average height ofapproximately 100 Å or less.
 19. The method as described in claim 18wherein a stiction value is lower than that obtained in a second systemhaving said features with said average height wherein said second systemcomprises a second slider without said texture thereon.
 20. A method ofoperating a disk drive comprising performing said method of claim 11.